Chapter 2: The Components of Matter

Vocabulary practice flashcards covering fundamental chemistry concepts from Chapter 2: classification of matter, laws of chemical combination, atomic theory, subatomic particles, isotopes, periodic table families, chemical formulas, and nomenclature.

Pure Substance

A form of matter composed of a single type of atom or molecule.

Mixture

Matter composed of two or more different types of atoms or molecules.

Element

A pure substance that cannot be chemically broken down into simpler substances.

Compound

A pure substance composed of two or more elements in fixed, definite proportions.

Homogeneous Mixture

A mixture whose composition is uniform throughout.

Heterogeneous Mixture

A mixture whose composition varies from one region to another.

Law of Conservation of Mass

A law proposed by Antoine Lavoisier in 1789 stating that matter is neither created nor destroyed in a chemical reaction.

Law of Definite Proportions

A law proposed by Joseph Proust in 1797 stating that all samples of a given compound have the same proportions of their constituent elements.

Law of Multiple Proportions

A law published by John Dalton in 1804 stating that when two elements form two different compounds, the masses of element B combining with $1\text{ g}$ of element A can be expressed as a ratio of small whole numbers.

Dalton's Atomic Theory

A theory developed in 1808 stating that elements are composed of tiny, indestructible particles called atoms, which combine in simple whole-number ratios to form compounds.

Cathode Ray Tube

A partially evacuated glass tube fitted with two electrodes through which cathode rays travel when a high voltage is applied.

Electron

A negatively charged, low-mass subatomic particle discovered by J. J. Thomson with a charge-to-mass ratio of $-1.76 \times 10^8\text{ C/g}$.

Millikan Oil Drop Experiment

A 1909 experiment that determined the fundamental charge of an electron to be $-1.60 \times 10^{-19}\text{ C}$, allowing the mass of an electron to be calculated as $9.10 \times 10^{-28}\text{ g}$.

Plum-Pudding Model

An early atomic model proposed around 1900 in which negatively charged electrons are embedded within a sphere of positive charge.

Rutherford's Gold Foil Experiment

An experiment performed in 1909 where alpha particles were directed at ultrathin gold foil, disproving the plum-pudding model and proving that atomic mass and positive charge are concentrated in a small nucleus.

Nucleus

The small, dense central core of an atom that contains all of its positive charge and most of its mass.

Neutron

A neutral subatomic particle located in the nucleus with a mass nearly identical to that of a proton ($1.67493 \times 10^{-27}\text{ kg}$).

Atomic Mass Unit (amu)

A unit of mass defined as $\frac{1}{12}$ the mass of a carbon atom containing 6 protons and 6 neutrons.

Atomic Number (Z)

The number of protons in an atom's nucleus, which uniquely defines the element.

Mass Number (A)

The total sum of protons and neutrons in an atom's nucleus ($A = \text{\# of protons} + \text{\# of neutrons}$).

Isotopes

Atoms of the same element with the same number of protons but different numbers of neutrons, resulting in different masses.

Natural Abundance

The percentage of a particular isotope found in a naturally occurring sample of an element.

Atomic Mass

The average mass of an element, calculated as a weighted average based on the natural abundance of each isotope.

Cation

A positively charged ion formed when an atom loses one or more electrons.

Anion

A negatively charged ion formed when an atom gains one or more electrons.

Periodic Law

Summarized by Dmitri Mendeleev in 1869, stating that when elements are arranged in order of increasing mass (or atomic number), certain properties recur periodically.

Metals

Elements located on the lower left side and middle of the periodic table that are good conductors of heat and electricity, malleable, ductile, shiny, and tend to lose electrons.

Non-metals

Elements on the upper right side of the periodic table that tend to be poor conductors of heat and electricity and tend to gain electrons during chemical changes.

Metalloids

Elements situated along the zigzag diagonal line separating metals and nonmetals that exhibit mixed properties.

Main-Group Elements

Elements whose properties tend to be largely predictable based on their position in the periodic table.

Transition Metals

Elements whose properties are less predictable based solely on their position in the periodic table and can form cations with varying charges.

Ionic Bond

A chemical bond resulting from electrostatic attraction between oppositely charged ions formed when a metal transfers electrons to a nonmetal.

Covalent Bond

A chemical bond formed when nonmetal atoms share electrons that interact with the nuclei of both atoms.

Empirical Formula

A chemical formula that shows the relative, simplest whole-number ratio of atoms of each element in a compound.

Molecular Formula

A chemical formula that shows the actual number of atoms of each element in a molecule of a compound.

Structural Formula

A diagrammatic representation showing how atoms in a molecule are connected or bonded to each other.

Atomic Elements

Elements that exist in nature with single individual atoms as their basic unit.

Molecular Elements

Elements that exist in nature as molecules composed of two or more bonded atoms of the same element.

Formula Unit

The basic, smallest electrically neutral collection of ions in an ionic compound.

Polyatomic Ion

An ion composed of a group of covalently bonded atoms carrying an overall net electrical charge.

Oxyanion

A polyatomic anion containing oxygen and one other element.

Hydrate

An ionic compound that contains a specific number of bound water molecules within its structure.

Binary Acid

An acid composed of a hydrogen atom and a nonmetal atom.

Oxyacid

An acid composed of a hydrogen atom combined with an oxyanion.

Hydrocarbons

The simplest organic molecules, composed exclusively of carbon and hydrogen atoms.